I don't really understand the concern. Seems to me the longer the overhang, the less likely you are to put your rear wheels in the water. I would certainly not dunk my motorhome, but have no issues launching our little 18' ski boat at normal launch ramps with our motorhome (that has ~10' overhang).
I do not put any part of the motorhome in the water, sometimes I have to winch the boat up a bit more than I'd like depending on steepness, but it works. On launch, a good rolling brake check releases the boat from the bunks nicely.
With 10k pounds on my rear wheels, slippage on the wet ramp is not an issue. I have traction issues when retrieving with my little Nissan Fronier 2wd, but not with the motorhome.
I have a front hitch, but have not yet used it for launching/retrieving. Only for carrying things. Seems like it would be a hassle to disconnect/reconnect to the rear hitch every time.
I generally have someone in the boat to drive it on/off so I never get out of the drivers seat, but for the rare occasion that I launch solo (be it in the pickup, or motorhome) I do have a rubber wheel chock on a long string that I put behind the front tire to be safe. I can then retrieve it remotely from the drivers seat when pulling forward.
